At just after 3:30 am ET, the European Space Agency’s Philae lander detached from the Rosetta spacecraft. 30 minutes later ESA officials received confirmation of the detachment. It takes 28 minutes for the signal from the spacecraft to reach Earth.

Described as “7 hours of Terror,” the whole world will know if the ESA was successful just after 11 am ET. Watch the attempted landing live below.

It has taken 10 years and more than 4 billion miles for the Rosetta mission to get to this point.

If all goes well, Philae will touch down on the comet’s surface and mission controllers will receive confirmation of landing at 11:02 am ET.

The biggest hurdle for Philae is obvious – the comet’s surface. Rosetta mission planners didn’t have the luxury of months, or years to find an optimal landing area. They had to wait for the Rosetta spacecraft to get to the comet first. From there, they had just six weeks to find landing zone candidates and then pick one. None of them are perfect, but the ESA picked a zone that had the best terrain. Flatter ground, fewer boulders, etc.

Rocks will be the biggest hazard. Now that Philae is heading towards the comet, there’s not much it can do in the way of steering.

Once it lands, Philae will shoot a harpoon at the surface to anchor itself. The gravity is so light on the comet, that without the harpoon, Philae would bounce around.

After a successful landing, Philae will being its initial 65 hour phase. During this nearly 3 day period, Philae will use 10 instruments, including cameras, a drill, and more to study the comet’s surface and its make-up.

If all goes according to plan, Philae will continue observations until March. That’s if there isn’t too much dust on the lander’s solar panels. Once March comes, the comet will be so close to the sun, it will damage the lander’s electronics.

Could comets have brought water to earth? That is just one question scientists hope to gain insights on from the comet. We’ll know in about an hour if Philae will be the one to offer answers.